Waste-derived aluminosilicate reinforcements in copper matrix composites for tribological applications: a critical review and future perspectives

Copper matrix composites (CMCs) have attracted considerable attention for advanced tribological materials. They combine copper’s excellent thermal and electrical conductivity with enhanced mechanical and wear performance from the reinforcing phase. Copper’s relatively low hardness and poor wear resistance limit its application under severe sliding conditions. This review critically examines recent advances in waste-derived aluminosilicate-reinforced copper matrix composites, with particular attention to calcined clay-derived metakaolin (MK) as an underexplored potential reinforcement. This review critically analyzes peer-reviewed articles published from 2020 to 2026 within the processing, microstructure, and tribological performance framework. To examine relationships among reinforcement parameters, microstructural evolution, fabrication routes, interfacial phenomena, wear mechanisms, and resulting mechanical, tribological, and functional performance. Although conventional ceramic reinforcements such as SiC, Al 2 O 3 , and TiC can enhance the mechanical and wear performance of copper composites, their production and processing increase the cost, energy, and environmental considerations. Waste-derived aluminosilicates such as fly ash (FA) and rice husk ash (RHA) offer waste valorization benefits and also reduce the dependency on conventional ceramic feedstocks. Metakaolin (MK) is a compositionally related option with a less experimentally established reinforcement pathway, whose performance in a Cu matrix needs direct validation. For example, increasing FA from 0 to 20 wt.% in a representative Cu–FA system increased hardness from 69 to 145 HV and reduced wear rate from 908 × 10 −5 to 479 × 10 −5 mm 3 /m and COF from 0.55 to 0.35, but reduced electrical conductivity from 80 to 32% IACS. Particle agglomeration, poor wettability, weak interfacial bonding, residual porosity, feedstock and processing variability, and concerns about the retention of copper’s inherent conductivity are the major challenges that continue to limit their broad application. Priority research needs include direct validation of Cu-MK systems, interface engineering, long-term tribological performance, reinforcement optimization, hybrid reinforcement systems, conductivity-performance trade-off assessment, and computationally assisted materials design. Overall, this review provides a materials science perspective for designing aluminosilicate-reinforced Cu composite through integration of processing, microstructure, tribological performance, functional property retention, and evidence of maturity.